This proposal will provide experimental information on the efficacy of various aspects of cellular support in patients undergoing chemotherapy for cancer. Humoral regulators of stem cell proliferation and maturation may influence the degree of toxicity with various chemotherapeutic agents. Both in vitro and in vivo assays are utilized to evaluate regulators and to establish their importance on circulating cellular components during chemotherapy. A model for experimental sepsis has been developed using Wistar/Furth rats. It has been shown that granulocyte transfusions protect against lethal sepsis when given prior to a septic inoculum. In the current year we will establish the value of platelet transfusions acting synergistically with granulocytes in the treatment of sepsis. Studies of autologous stem cells obtained from the peripheral blood and from the bone marrow will be performed to determine their usefulness in supporting patients receiving treatment with drugs resulting in prolonged myelosuppression (e.g., methyl CCNU, Busulfan, etc.). These investigations are designed to contribute to the understanding of factors which critically influence the success of current support programs. BIBLIOGRAPHIC REFERENCES: Roy, A.J., Yankee, R.A., Brivkalns, A. & Fitch, M.: Viability of granulocytes obtained by filtration leukopheresis. Transfusion 15:539-547, 1975. Richman, C.A., Weiner, R.S. and Yankee, R.A.: Increase in Circulating Stem Cells Following Chemotherapy in Man. Blood 47:1031-1039, 1976.